Power transmission



Oct. 5, 1943. F. T. HARRINGTON 2,331,026

POWER TRANSMISSION Filed July 5, 1940 76 ATTORNEY Patented Oct. 5, 1943 POWER TRANSMISSION Ferrisv T. Harrington, Detroit, Mich., assignor to Vickers Incorporated, Detroit, Mich., a. corporation of Michigan Application July 5, 1940, serial No. 343,969

(ci. so-52) 2 Claims.

This invention relates to power transmissions, particularly to those of the type comprising two or more uid pressure energy translating devices one of which may function as a pump and another as a fluid motor.

The invention is more particularly concerned with a power transmission system incorporating a diierential-area cylinder-and-piston moto;` together with control means for directing fluid to the opposite ends of the motor to produce feed and rapid-traverse movement with highest eiciency. In many classes of machine tools, for examples, shapers, planers, and broaching machines, it is desirable to utilize a feed movement in one direction and a rapid-traverse movement in the other direction. At the same time it is likewise desirable to have the feeding movement take place in that direction in which the piston rod is in tension. This means that during the feeding movement, when the work to be done is usually the heaviest, the oil is fed into the small end of the cylinder where a given volume of uid will produce a greater piston movement than in the large end. This drawback has heretofore been overcome by connecting both ends of the cylinder together during the return stroke so that the fluid discharged from the small end is added to the volume supplied to the large end. Such a system, however, does not provide independent control of the speed of movement in one direction as compared to that in the other direction where a fixed displacement pump is utilized as the source of supply.

Another method of providing for rapid-traverse and feed rates with a fixed displacement pump utilizes a flow-rate controlling mechanism for providing a reduced rate of uid supply during the feeding movement, the excess volume delivered by the pump being by-passed without doing? effective work. Systems of this character permit of ready control of the feeding speed without affecting the rapid return speed but have not heretofore utilized a differential cylinder action.--1f-1yr It is--anobject of the present invention to provide aniinproved power transmission system for operating a differential piston-and-cylinder motor in which the advantages of both methods of obtaining feed and rapid-traverse movement are utilized. l

Furthervobjects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is'clearly shown.

In the drawing:

Figure 1 is a diagrammatic view of a power transmission system incorporating a preferred form of the present invention.

Figure 2 is a sectional view of the valve mechanism shown in Figure 1 illustrating the parts in a different position.

Figure 3 is a view corresponding to Figure 2 showing the parts in a third position.

Referring now to Figure 1, there is illustrated a differential-area piston-and-cylinder motor comprising a cylinder I0 having a piston I2 therein provided with a rod I4 projecting from one end of the cylinder. Fluid conduits I6 and I8 connect between'the small and large ends, respectively, of cylinder I0, and a pair of cylinder ports 20 and 22 provided in a directional control valve designated 24.

For the purpose of supplying uid to operate the motor I8 a fixed displacement pump 26 is provided and is driven by a suitable prime mover such as an electric motor 28. A suction conduit 30 serves to supply oil from a tank 32 to the inlet of the pump 26. The pump 26 has its outlet connected with a supply conduit 34 which leads to one pressure port 36 in the valve 24.

A branch conduit 38 connects with the conduit 34 and extends to a combined flow-control and relief valve 40. The latter may be similar in construction to 'that illustrated in the patent to Harry F. Vickers, No. 2,102,865. This valve provides a through connection between conduit 38 and a conduit 42 which extends to a second inlet port44 of the valve 24, this path being'restricted, however, in varying degree, depending upon the adjustment of a manually controlled throttle 46. The valve 40 is provided with an overflow port 48 which connects to the tank 32 by a conduit 58.

A balanced piston valve` 52 is automatically controlled to regulate the quantity overflowing through the port 48 to the amount necessary to maintain a predetermined pressure drop across the orifice 46. In addition, a pilot relief valve 54 provides for a maximum pressure limit on the oil in conduits 38 and 42.

The valve 24 is provided additionally with a return port 56 which is freely open to tank through the branch conduit 58 connected with the conduit 50. It is also provided with a second return port 60 which leads tothe tank through a back-pressure valve 62. The latter may be similar in construction to that illustrated in the patent to Kenneth R. Herman, No. 2,200,824, and serves to maintain a predetermined back pressure on oil returning from port 60 to the tank 32.

For the purpose of identifying the various ports in the valve 2l they are hereafter designated inthe claims as follows: Porti! is re- :rred to ss s am inlet port. while port u is referred to as a second inlet port. In a similar f operating positions by means of any suitable operator such as the manual lever l0. A.spring pressed detent l2 may be provided for retaining the-valve-frictionally in either one of its three effective positions.

Y ,In` operation, starting with the parts in the position illustrated in Figure l, and with the pump 2l and-motcr 28 operating, it will be seen that oil' will bewithdrawn from the tank through suction conduit 2l and delivered through conduit #utc-portie of valve 24. Port 2l is in communication with port It through the central bore 1I so that the whole pump delivery is effectively bypassed back to the tank through conduits Il and 50, this path imposing negligible resistance so that the -pumpis effectively unloaded. In this position of the spool N, both of the cylinder ports 2li and 22am-blocked by the lands 12 and B8, respectively. l f

In' order to start the piston I2 moving to the left-on a feeding stroke, the valve spool Il may be shifted to the right into the position illustrated in Figure 2. Y The land 88 now blocks the supply port 26, while the'. supply port Il is connected to the cylinder port 20'.' 'Oil is accordingly delivered at a rate determined bythe setting of throttle 45 to the vcylinder conduit It and the small end .of cylinder I0. Piston i2k accordingly moves to the left discharging oil from the large end of the .cylinder through .conduit I8, port 22, port 60, and conduit'i and valve 82 tothe tank. It will thus be seen that the piston I2 will accord.- ingly move to the left-at apredetermined rate, the back-pressure valve 62 preventing any jerky operation in case the load should rapidly fluctuate.

When it is desired to return the piston i2 to the right, the'valve spool 6l may be shifted completely to-its lefthand position as illustrated in Figure 3. In this position the second supply port Il is blocked by the land 12. The Ist supply port is opened to the cylinder port 22 so that the full pump delivery is freely delivered through conduit I8 to the large end of cylinder I0. The piston I 2 accordingly moves to the right independent of adjustment at the throttle 4t. This feature is particularly desirable `with machine tools such as planers and shapers where varying requirements of the work necessitate widely different speeds on the feed part of the cycle. On the return stroke, however, which is always an idle stroke, the maximum possible speed ls desirable. Thus, the present circuit provides for producing the rapid return stroke by utilizing the full volume of the pump 2t over the smallest net area at the motor which its pressure rating will permit.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted. all coming within the scope of the claims which follow. Y

What-is claimed is as follows:

l. Ahydraulic power transmission system comprising in combination a differential-area pistonand-cylinder motor, a pump for supplying fluid to the motor, a three-position, six-port valve for controlling the flow of fluid between the pump and motor, a direct connection between the pump discharging oil from the small end through con- "duit I6 to port .20. The latter is in communication with ports 28 and 22 through the central bore 16 so that this volume of oil joins with the pump delivery in propelling the piston I2 to the right.

and a first inlet port of the valve, a connection including a flow-rate controller between the pump and a second inlet port of the valve, open exhaust line from a first outlet port o ,the valve, a restricted exhaust line from a second outlet port of the valve, connections leading respectively from the ends of the cylinder to a pair of motor ports of the valve, a movablel valve member having lands and recesses to selectively place said ports in communication with one another, said ports, lands and recesses being arranged to provide a rate-controlled forward motor stroke by connecting the second inlet port with the small-end motor port and the second outlet port with the large-end motor port, a differential rapid return by connecting the first inlet port with both motor ports and blocking the'second inlet port, and a stop by connecting-the first inlet port with the nrst outlet port.

2. A hydraulictpower transmission system comprising in combination a diEerential-area pistonand-cylinder motor, a pump for supplying fluid to the motor, a three-position, six-port valve for controlling the flow of fluid between the pump and motor, a direct connection between the pump and a ilrst inlet port of the valve, a connection including a flow-rate controller between the pump and a second inlet port of the valve, an open exhaust line from a first outlet port of the valve, a restricted exhaust linefrom a second outlet port of the valve, connections leading respectively from the ends of the cylinder to a pair of motor ports of the valve, a movable valve member having lands and recesses to selectively place said ports in communication with one another, said ports, lands and recesses being arranged to provide a rate-controlled forward motor stroke by connecting the second inlet port with the smallend motor port and the second outlet port with the large-end motor port, a differential rapid return by connecting the ilrst inlet port with both motor ports and blocking the second inlet port, and a stop by connecting the first inlet port with the rst outlet port, said movable member having an internal connection between two otherF wise separated recesses and serving to conduct opierating fluid in at least two positions of the va ve.

FERRIS T. HARRINGTON. 

